Examination of key factors determining the catalytic performance of Zn-Ga/HZSM-5 bifunctional catalysts and establishment of reaction network in alkylation of benzene with carbon dioxide

Alkylation of benzene with carbon dioxide (CO 2 ) is significant for converting greenhouse gas and surplus benzene into value-added toluene and xylene. Herein, a bifunctional catalyst comprising Zn/Ga oxides and HZSM-5 zeolite was developed to efficiently promote the methylation of benzene with CO 2 and H 2 . This catalytic system exhibited excellent performance at 425 ℃ and 3.0 MPa, through which benzene conversion of 39.1% and total xylene/toluene selectivity of 92.7% have been achieved. Furthermore, the catalysts are carefully characterized; compositions of Zn/Ga oxides and Si/Al ratios of HZSM-5 zeolite are recognized as decisive factors for reaction activity and selectivity respectively. Additionally, primary reaction pathways are explored and testified to provide detailed understanding for the establishment of reaction networks, especially for mechanisms of ethylbenzene evolution. These findings are able to provide more deep insights into the process of benzene alkylation, which further facilitates the emergence of effective catalysts with potential industrial applications.